PROJECT SUMMARY/ABSTRACT Two groups that are under-researched but at the highest risk for problems stemming from opioid use disorder are (1) public system-involved emerging adults (EAs; ages 16-25) and (2) individuals who are justice- involved (including EAs). Compared to all other age groups, EAs report the highest rates of drug use, including use of opiates, and public system-involved EAs are more likely to have negative outcomes. For adults of all ages, opioid use results in a 13-fold increased probability of justice system contact. And, among the prison re-entry population, the leading cause of death is overdose, mostly from opioids. Further, polysubstance use is nearly universal for EAs and justice-involved adults (of any age) using opioids. Peer recovery support services and recovery residences are proliferating nationally and may have tremendous benefit for these two high-risk groups, but research on them is limited and lacks scientific rigor. The ultimate goal of this Initiative is rapid advancement of the recovery support services field through developing actionable research such that continued network funding will no longer be necessary to sustain growth. To accomplish this, it is essential to identify and equip investigators willing to dedicate or redirect their research efforts to this topic. However, a fundamental challenge for evaluating recovery support services (and any other community-based program) is the inherent incompatibility of rigorous research methods and the context of real-world services efforts. This requires adaptation or development of innovative and comprehensive methods that thoughtfully combine adaptable designs, advanced measurement, and sophisticated statistical analyses. Investigators also must be competent and well-trained to collaborate with community stakeholders so that rigorous research can be conducted in real- world settings. Optimally, though, people impacted by recovery support services and the research conducted on them must help drive the research agenda; rather than priorities being researcher-initiated, persons in recovery from the target populations and stakeholders in that community (recovery support service providers and payors) must be effectively engaged. Thus, this Initiative is a partnership between advanced researchers, persons in recovery from the target high-risk populations, providers, and payors. The Initiative will advance research on the efficacy/effectiveness of peer recovery supports and recovery residences for public-system involved emerging adults and justice-involved adults with opioid use disorders and medication assisted treatment experience through ambitious but achievable goals: (1) identify priority areas of research via engaging individuals in recovery and providers/payors, (2) grow the field of skilled early career investigators focused on this research, (3) provide seed funds and guidance to produce preliminary studies for NIH funding, and (4) conduct dissemination and outreach to the larger field. With these aims, the Initiative is poised to be a catalyst that provokes rapid expansion in the number of skilled investigators and high-quality research tackling this critical public health issue.